docs: def import_tracks(self, import_tracks):
          """
          Add the given tracks/track to the corpus.
          If any of the given track-ids already exists, a suffix is appended so it is unique.
  
          Args:
              import_tracks (list): Either a list of or a single :py:class:`audiomate.tracks.Track`.
  
          Returns:
              dict: A dictionary containing track-idx mappings (old-track-idx/track-instance).
                    If a track is imported, whose idx already exists this mapping can be used to check
                    the new id.
          """
  
          if isinstance(import_tracks, tracks.Track):
              import_tracks = [import_tracks]
  
          idx_mapping = {}
  
          for track in import_tracks:
              idx_mapping[track.idx] = track
  
              # Add index to idx if already existing
              if track.idx in self._tracks.keys():
                  track.idx = naming.index_name_if_in_list(track.idx, self._tracks.keys())
  
              self._tracks[track.idx] = track
  
          return idx_mapping